1. Field of the Invention
The present invention relates generally to pipe joints in a pipe string and more specifically, to a plate-indicator position make-up method to accurately determine the position make-up of connections on pipe, such as the couplings used on oil field tubular goods.
2. Description of the Prior Art
A wide variety of drill pipe, tubing and casing (tubular goods) for oil and gas drilling, completion, production and stimulation activities are available at the present time. In the case of sections of such tubular goods used in the oil field (for example long sections of well casing or tubing), such sections of pipe usually have a tapered, exteriorly-threaded male end called a pin member. Such pin members are threaded into couplings, collars or integral female pipe sections, having threaded ends referred to as the box member. These box members have an interiorly-threaded tapered thread surfaces corresponding to their respective pin members for mating with the pin members to form threaded connections.
One type of connection for these joints is the American Petroleum Institute (“API”) threaded and coupled connection that achieves its assembly without torque shoulders. These tapered connections provide increasing bearing stresses to provide the seal between the pin member and box member with increasing engagement produced by rotational torque. It is well known in the petroleum industry that the performance of an API connection is highly dependent on the make-up assembly (engagement) condition of the joint, and therefore it is important to determine if the joint is made-up properly. A number of factors can affect the integrity of the assembly process, including friction-related factors such as thread dope, plating type and thickness, surface finishes, eccentricity, ovality, impurities (dirt or rust) and external factors such as stab alignment and wind loading that occur at the well site.
A number of methods have been used in the prior art in order to monitor and control make-up of oilfield tubular connections. One type of method is the “torque-only” method based upon the read-out of a load cell attached to the joint or power make-up tongs and calibrated for torque. This method has limitations because it does not provide enough information to distinguish quality control problems such as out-of-tolerance threads, cross-threading, or galling in every situation.
A second method, “torque-turn”, requires sophisticated electronics including a computer and sensors to monitor both the torque and turns which add to operational costs and delay the running time of the pipe sections. The “torque-turn” method is extremely sensitive to a reference torque which is a relatively low value, typically 10 percent of the minimum torque. This torque is sometimes determined by API torque recommendations. After this reference torque is reached, a predetermined number of turns are counted in the make-up of the tubular connection. If a false reference torque occurs to activate the turn counter because of one of the above described quality control problems or assembly conditions, an improper Joint make-up will result.
A third method is where the torque imposed on premium thread connections between tubular joints is monitored and plotted as a function of time rather than the number of turns. In this manner, the torque can be detected at the time metal-to-metal sealing contact is achieved during make-up of the connection. Further, torque response of the connection may be monitored after shouldering occurs.
Despite the above advances, there has been a long-felt need in the oil and gas industry for a simplified method of determining in the field the integrity of such joint make-up visually, thereby avoiding the need for complex instrumentation such as used in the “torque-turn” or “torque-time” methods or the need for elaborate calibration methods for the instrumentation involved. Proposed methods have included the use of barrettes, measuring from the open end of the pipe and the use of a permanent mark on the outer diameter of the pipe. Each of these techniques has some disadvantage. The barrette method is highly accurate but only works on hooked threads. Measuring from the open end may not be possible with some bucking units and is troublesome and may easily result in mistakes. The use of permanent mark on the OD can delay production in applying the mark and location control may not be very accurate.
As a result, even while using these above methods for making up joints, problems still continue to arise and the industry still suffers problems when forming such joints. These problems include influent and effluent pipe leakage because of lack of good sealing in improperly made-up joints. The following references are typical of other attempts in the prior art to solve the above described problems, but should be understood as being only representative of the prior art in the field. Each of these references primarily deals with a method for properly torqueing a threaded pipe connection.
U.S. Pat. No. 4,962,579 teaches a method for visually determining on the rig floor if a joint is properly made up with the right amount of torque. A registry mark is placed on the exterior of the first pipe section for proper axial engagement of the pin member with the coupling or box member. The position is determined by finite element analysis.
U.S. Pat. No. 5,212,885 shows a method for achieving proper sealing positioning and proper make up torque of threaded pipe sections. If the face of the box member is properly positioned relative to a triangle mark on the pipe section, make up is terminated. If the face has not reached edge of the triangle mark, torque is increased until either the face progresses into the body of the triangle mark or until maximum torque occurs.
U.S. Pat. No. 4,614,120 shows a method for determining proper make-up torque for pipe joints. A reference mark is set on the male element and on the female element. A grease is applied to the joint and the joint is made up using sufficient torque to cause one element to rotate with the respect to the other element. The joint is torqued until one element reaches a predetermined angle beyond the point where the reference marks are facing each other. This operation is repeated with a determination being made of the range of torques to be applied to the joint with a particular grease being utilized.
U.S. Pat. No. 5,661,888 shows an apparatus for positing two threaded pipes within a target range of relative axial positions. The device supposedly offers advantages over using visual “bench marks” placed on the pin and box members. The device includes a sensor and calibrating device for positioning the sensor a calibrated distance from the end of one of the pipes. A signal generator generates a signal once the sensor head indicates that the relative axial position of the pipes are within the target range desired.
A need continues to exist, therefore, for an improved method for determining the position make-up of connections on pipe, such as couplings used on oil field tubular goods and similar connections.